The feature generation process in eq. REF  can be considered a generalized version of self-attention [1]}. The self-attention pools values \(\mathbf {V}\)  depending on the affinities obtained by computing similarity between the query \(\mathbf {Q}\)  and key \(\mathbf {K}\) , are formulated as
\(\mathbf {Y}_{i,j,k}=\sum _{(p,q)\in \Omega }(\mathbf {QK}^\top )_{i,j,p,q,\lceil kH/C\rceil }\mathbf {V}_{p,q,k},\) 
